Title

Greater Melbourne LiDAR - Difference DTM 

Resource Type

Dataset  

Spatial representation type

Grid  

Horizontal Accuracy

0.4m  

Code

MGA Zone 55 GDA94 

 

Title

ESRI Ascii 

Topic category

• Elevation

Use limitation

General 

Classification

Unclassified  

Description

A difference analysis was carried out over the entirety of the dataset in comparison to a series of historical DTM datasets covering the same area (summarily described as 2009 Melbourne DTM data). Difference rasters were calculated on an Old Minus New methodology in order to calculate summary statistics. This means that when viewing the difference raster, a negative value represents a cell which appeared higher in the 2018 dataset than the 2009 data, and a positive value represents a cell which appeared lower in the 2018 dataset than the 2009 data. Analysis was done on a per 1km x 1km tile basis, meaning that on average each tile summarises the values of approximately 1,000,000 individual DTM values, each of which is the averaged value of approximately 8 LiDAR measurements, meaning these summary statistics are a broad measure only. For more accurate assessments of the absolute accuracy of each individual section of the dataset, comparison checks have been carried out throughout the QA4LiDAR process and should be used for an accurate assessment on a per site basis. Having said this, the difference analysis is a useful tool for the assessment of the overall difference of the dataset in comparison to previously collected data. 

Classification

Unclassified